This application relates to the treatment of spun yarns, and more specifically to the preparation of the yarn by securing the otherwise extending fiber ends to the yarn body, melt sizing the yarn and preparing it for weaving or knitting operations on equipment that was previously only used to weave or knit continuous filament yarns. Spun yarns so processed may now be woven or knit efficiently on equipment previously restricted to continuous filament yarns.
Continuous filament styles are subject to seasonal styling fluctuations, and because of these unavoidable seasonal styling limitations, looms are idle at various times. Conventional wisdom indicates that spun yarn cannot be successfully woven or knot on equipment intended for continuous filament yarns because the amount of shedding eventually requires the equipment to be shut down and cleaned. Conventional spun yarns woven on a water jet loom cause lint to be collected by the water on various loom parts, and when the quantity of accumulated lint becomes large enough, it is transferred to the fabric. When this occurs, it is necessary to stop the loom and remove lint deposits at a frequency that becomes economically unfeasible. Similar conditions apply in warp knit operations. Not only does lint shedding cause fabric defects, but protruding fibers cause adjacent ends to roll which may result in dropped stitches. Thus, these undesirable conditions limit warp knit spun yarn styling.
It is commmercially feasible to warp knit staple yarns spun from cotton or polyester/cotton, but at normal knitting speeds the knitted fabrics that are produced contain an intolerable number of defects. For example, fabrics warp knitted from 50/1 Supima cotton yarns at normal speeds were found to contain an average of 4.9 defects (including dropped stitches caused by lint, stop marks, etc.) per hundred square yards. In addition, stop marks often affect the fabric appearance on the side of the machine opposite the side on which the defect occurred. Reduction of the number of fabric defects to a number like 3 to 4 per hundred square yards would greatly improve the market for warp knit spun fabrics. Such results are now made possible by the process of this invention.
This invention provides a spun yarn whose lint is prevented or inhibited from shedding on the fabric production equipment, and thus quality and production problems are avoided because of the absence or substantial absence of spun yarn lint. As a consequence, the number of times the equipment needs to be stopped for cleaning is reduced to an acceptable, economic level and the fabric formation equipment used for various stylings becomes more flexible. In addition, the process provides a means for efficiently weaving staple yarns as the filling on a water-jet loom, with a low amount of shedding and lint accumulation. Staple yarns, such as cotton, can now be run efficiently on warp knitting machines with only a low amount of shedding and greatly reduced defects, resulting in the ability to produce novel, highly attractive new products.
In the process of this invention, spun yarn is passed through a vortex air jet nozzle in which the fiber ends that extend outside the body of the yarn, sometimes referred to as yarn "hairiness", are laid down against the yarn body. The vortex air jet nozzle also serves to orient the spun yarn and configure it just prior to being contacted with hot melt size as presented to the yarn in a grooved applicator roll or other convenient size distributing equipment. The vortex air jet nozzle is used to wrap producting staple fibers around the yarn bundle while at the same time the path of the yarn bundle is "ballooned" in that the yarn assumes a shape resembling that of a standing wave in a violin string after it has been rubbed by the violin bow. The vortex action also causes false twisting of the yarn as the yarn enters the grooved size applicator roll. This ballooning technique has the unexpected benefit of permitting the yarn to wipe not only the bottom of the groove of the melt size applicator roll, but the walls of the groove as well permitting a much lower size add-on as the ballooning action serves to spread the hot melt size more uniformly over the yarn surface. Placement of the vortex air nozzle with respect to its distance from the grooved size applicator roll is adjusted to allow for maximum efficiency and control of size add-on as well as reducing the amount of lint generated during the process to an acceptable, economic level.
Significant is the fact that relatively small amounts of melt size are applied to the yarn, certainly amounts different from hot melt warp sizing of yarns used for weaving. Conventional hot melt warp sizing requires about 5% or more of melt size to be applied to the yarn. In contrast, the two part interactive system of this invention wraps protruding staple yarn fibers around the yarn bundle, configures the yarn bundle for efficient melt size pick-up and immediately "glues" the protruding staple fibers into place by the application of a very modest amount of hot melt size. Not only does the vortex nozzle wrap the fibers around the yarn bundle, it also serves to false twist the yarn, and causes it to balloon, thus positioning it for maximum efficiency and minimum but effective size pick-up as the body of the yarn enters the grooved roll. This permits quantitatively lower size pick-up, calculated as add-on or additional weight to the weight of the yarn, and serves to spread the hot melt size over the surface of the yarn more uniformly while minimizing discharge of extraneous yarn lint products.
A vortex action fluid nozzle suited for the process of this invention is described in detail in co-pending, commonly-assigned U.S. application Ser. No. 719,129 filed Apr. 2, 1985, the disclosure of which is hereby incorporated by reference. The grooved melt size applicator roll is of a type illustrated in commonly-assigned U.S. Pat. No. 3,990,132, the disclosure of which is also incorporated by reference.
It is the primary object of the present invention to provide a procedure and equipment for reducing yarn hairiness and applying an optimum, but reduced amount of melt size in a simple, effective manner. Additional objects of the invention include the use of spun yarns so treated for weaving fabrics on a water jet loom and for knitting fabrics on warp knitting machines. In warp knitting, the hot-melt-sized yarns of this invention can serve either as the warp yarns themselves, or as laid-in yarns in either the wrap or filling direction. In particular, the invention permits the textile manufacturer to construct fabrics from sources other than continuous filament yarns, for instance cotton, wool or other non-synthetic fibers. These and other objects of the invention will become clear from this specification, an inspection of the detailed description of the drawings, and from the appended claims.